ipn/ipnlocal: handle untagging nodes better

We would end up with duplicate profiles for the node as the UserID
would have chnaged. In order to correctly deduplicate profiles, we
need to look at both the UserID and the NodeID. A single machine can
only ever have 1 profile per NodeID and 1 profile per UserID.

Note: UserID of a Node can change when the node is tagged/untagged,
and the NodeID of a device can change when the node is deleted so we
need to check for both.

Updates #713

Signed-off-by: Maisem Ali <maisem@tailscale.com>

types/persist/persist.go

@@ -38,6 +38,7 @@ type Persist struct {
 	LoginName         string
 	UserProfile       tailcfg.UserProfile
 	NetworkLockKey    key.NLPrivate
+	NodeID            tailcfg.StableNodeID
 }
 
 // PublicNodeKey returns the public key for the node key.
@@ -68,7 +69,8 @@ func (p *Persist) Equals(p2 *Persist) bool {
 		p.Provider == p2.Provider &&
 		p.LoginName == p2.LoginName &&
 		p.UserProfile == p2.UserProfile &&
-		p.NetworkLockKey.Equal(p2.NetworkLockKey)
+		p.NetworkLockKey.Equal(p2.NetworkLockKey) &&
+		p.NodeID == p2.NodeID
 }
 
 func (p *Persist) Pretty() string {